Monday, April 25, 2022

Earth Day Geology Conversations

It is really heartening to see students take an initiative in outreach. The Science Paradox is one such science outreach effort.  Do take a moment to browse through their website and subscribe to their newsletter.  

For this Earth Day 2022, they invited me for a conversation about geology. The interview was conducted by Anaya Tiwari and Bhargavi Nerikar.  We talked about my decision to take up geology, the importance of geosciences, the role of outreach, books, and my parallel existence as a sports coach.

The conversation has been broken up into seven short videos. I am embedding the section on Geotourism below. 

The complete set of links to the interview are as posted.

1) What drove you towards pursuing geoscience?

2) Importance of geosciences.

3) How do you think geosciences can be incorporated in our education system?

4) What are  your thoughts on science outreach in reaching the masses and how effective that is?

5) Science outreach through geotourism.

6) Book recommendations for the field of geology.

7) What was the motivation to shift from academia to sports coaching?

 It was fun!

Thursday, April 21, 2022

Neglected Children Of The Sea Floor

Carl Simpson and Jeremy B.C. Jackson, in an essay titled Bryozoan Revelations for Science Advances, sketch out the important biological aspects of bryozoans, a type of marine invertebrate. 

From their article: 

"Bryozoans are neglected children of the sea floor. Google corals and you get nearly 4 billion hits, whereas bryozoans get just 4 million. This disparity reflects the enormity and notable beauty of coral reefs and extraordinary diversity of associated species that have long attracted intense scientific research. Yet for all their grandeur, corals occupy less than a tiny fraction of 1% of the global ocean, whereas bryozoans extend from the equator to the poles and intertidal to abyss. Bryozoans are species-rich. As a group, they have at least 10 times more species than corals. They also have a more extensive and continuous fossil record and have been major components of vast seafloor communities for half a billion years".

The enormous diversity of bryozoan skeletal shapes and their abundance as living communities and as fossils from the late Cambrian onwards make it possible to use them to understand evolutionary questions such as timing of origins, rates of change, convergent evolution, and origin of variable form in animal communities. This succinct essay summarizes these lines of research quite well.

As a sedimentologist my interest in these organisms was the role they played as sedimentary particles. Bryozoans, along with echinoids and brachiopods, were among the most common sea floor inhabitants of Paleozoic shallow marine realms. They made up a large proportions of the sediment that formed by the disintegration of shells and skeletons of sea creatures.  

A typical bryozoan skeleton has a trellis like appearance. Bryozoans are colonial organisms building a lattice like structure with the animal living in chambers called zooids. It is these zooids that was my main interest, or rather what I could see inside them. The animal was long gone, decayed away, but the chamber or cavity was filled with different types  of calcite, archiving the process of the transformation of loose sediment into rock. Through geologic history different types of fluids had entered the open spaces within the skeleton and precipitated different types of calcite. Petrologists can infer the changing geochemical conditions as sediments get buried and importantly trace the changes in open spaces, or porosity, as fluids either dissolve sediment or deposit new minerals, information that is useful to the petroleum industry.

I will share a couple of examples of these diagenetic changes observed inside a zooid.

This thin section of a limestone from the Middle Ordovician strata of the southern Appalachian mountains has been stained using a mixture of Alizarin Red-S and Potassium Ferricyanide. The pink is an iron free calcite. The purple in the center of the zooids is an iron rich calcite. This sequence from an iron free to an iron rich calcite indicates oxygen poor reducing conditions upon burial, a chemical environment in which iron can enter the growing calcite crystal.

And in this thin section the pale bronze colored mineral highlighting the skeletal frame is chert, a variety of silica that has partially replaced the calcite skeleton. The replacement process has been quite delicate, preserving the original structure of the skeleton.

Evolution is not the only story that bryozoans reveal.

Wednesday, April 20, 2022

Kolar Gold Field

Geology and Livelihoods #19

I came across this excellent documentary on the Kolar Gold Field via Twitter. The film is directed by Basav Biradar and produced by Sahapedia.

Email subscribers who are unable to see the embedded video can watch it here- In Search of Gold.

Like many established mining towns, Kolar too saw generations of the same family work in the mines. Son followed father into the dark shafts. Mining provided employment, but it was dangerous back breaking work. The documentary highlights the lives of workers and their struggle for better work conditions. 

Kolar gold is late Archaean in age with mineralization taking place between 2700-2500 million years ago. There are two types of deposits. There is a "stratiform sulphide type", so called because the gold bodies are contained within iron sulphide rich volcanic and sedimentary layers. These deposits formed on the sea floor contemporaneous with volcanism and sedimentation. The second type is a hydrothermal deposit wherein mineralizing fluids mobilized and precipitated gold in veins along N-NE oriented fracture zones. This mineralization event occurred at a later stage when magmatism and metamorphism affected the host terrain.

But do watch this for the many personal stories of the people who worked the mines.